U.S. officials say one American has died in the hostage standoff at an Algerian gas complex.

The officials say the deceased American is a Texas resident, Frederick Buttaccio. It is unclear how he died.

The officials say Buttaccio's remains have been recovered and his family has been notified.

The officials spoke on condition of anonymity because they weren't authorized to speak publicly on the matter.

Earlier version:

Algeria's state news agency says 12 hostages have been killed since the start of the operation to free workers kidnapped by Islamic militants at a natural gas plant in the Sahara.

The APS news agency quotes an unidentified security source for the new death toll and says the fatalities include both Algerian and foreign workers at the remote desert facility.

APS also said Friday that 18 of the hostage takers have been killed.

The same news agency said earlier that nearly 100 out of the 132 foreign hostages kidnapped by Islamist militants have been freed from a gas plant in the Sahara desert.

The report by APS indicated a potential breakthrough in a bloody siege that began when militants seized the plant early Wednesday and reflected a significant jump in the number of foreign hostages involved.

The Friday report from the government news agency, citing a security official, did not mention any casualties in the battles between Algerian forces and the militants. But earlier it had said that 18 militants had been killed.

It was not clear whether the remaining foreigners were still captive or had been killed in the Algerian military operation to free them that began Thursday.

Militants claimed that military helicopters opened fire Thursday when they were transporting hostages from the living quarters to the main factory area, and that 35 hostages and 15 militants died in the strafing.

A Mauritanian news site that frequently receives messages from al-Qaida linked militants said the hostage-takers in Algeria had offered to trade two captive Americans for two jailed terror figures in the United States.

One of the two, Omar Abdel Rahman, masterminded the 1993 World Trade Center bombing.

Panetta: US-British working to free hostages

Defense Secretary Leon Panetta says the U.S. is working with the British and Algerian governments to assess what's happening on the ground at a natural gas complex in the Sahara where Islamic militants are holding hostages from at least 10 countries.

The fate of many of the captives remains uncertain.

Speaking Friday at Kings College in London, Panetta said the U.S. is "working around the clock to ensure the safe return of our citizens."

Panetta says the terrorists should be on notice that they'll find no sanctuary in Algeria or North Africa.

He says anyone who looks to attack the U.S. will have "no place to hide."

The Pentagon says Panetta will meet with British Prime Minister David Cameron.

They will discuss Islamic militant operations in Mali and Algeria.

Here's a summary of the latest information on the hostages:

- ALGERIA: Hundreds of Algerians worked at the gas plant, but the Algerian media say most were released.

- UNITED STATES: Seven Americans were hostages, the militants said, but they claimed only two survived the Algerian strafing Thursday. A U.S. official said late Thursday that while some Americans escaped, other Americans remain either held or unaccounted for.

- BRITAIN: British Prime Minister David Cameron says 30 Britons were unaccounted for Thursday but that number is now "significantly reduced." One Briton was confirmed killed in the initial attack on Wednesday.

- JAPAN: JGC Corp, which provides services at the complex, confirmed seven Japanese employees were safe and 10 others were unaccounted for. Ten non-Japanese employees are also alive, it said.

- PHILIPPINES: Algeria's state news agency said two Filipino hostages were killed. Philippine Foreign Affairs spokesman Raul Hernandez said Friday at least one Filipino escaped with injuries during the military operation and he had no information about any fatalities.

- MALAYSIA: Two Malaysians were held, the government says.

- IRELAND: A 36-year-old Irish electrician was among the hostages but managed to escape.

- FRANCE: President Francois Hollande said there are French hostages but gave no exact number.